[Haskell-cafe] DiscreteMap

In addition to the former discussion: http://www.haskell.org/pipermail/haskell/2002-October/010629.html Has someone thought about a type class that provides a uniform interface to Array and FiniteMap? The difference to a general Function class is that a DiscreteMap could return its domain, that is the list of all of its keys/indices/arguments.